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What does the C* (Cstar) parameter demand ?(A320)
I have been reading a LOT of research papers and many articles, but none of them tell how the C* parameter in Airbus is used for the vertical augmentation of the aircraft.
I am aware that with a deflection in sidestick, a G-load is demanded through a COM channel
{(-1,+2.5) -> in clean config} but I have many questions :

What is the relation of this G-load demand with the Load factor(Nz) and C* ?
I know that C* = Nz + (Vco * Q)/g, where Vco for A320 is 210 knots, how is this computed C* parameter used ?
What is the final parameter that can be used for demanding an elevator deflection through a controller?
What control structure lies between the G-load demand and the final elevator deflection?
I want to know the proper Math behind it.

Many people have no idea about all this and keep spreading misinformation on various platforms because of which I got extremely deviated from the right information so I am here asking these questions :)
Thank you

"I am aware that with a deflection in sidestick, a G-load is demanded [...]"

Not exactly. A C* is demanded, not G-load. A given deflection of the sidestick corresponds to a C* demand. Then the controller simply targets that C* demand. Answer to questions 3 and 4 probably involves airbus proprietary data.

C* is easier to understand if you start with pure g-force control. The basic components are:

The control stick, where the pilot commands a load factor in the -1.0 to 2.5 range.
The accelerometer, which measures the actual load factor in the body-z-direction.
A PID controller, which controls elevator deflection so that measured load factor always matches the pilot's command. The P, I, and D gains in this controller are not considered part of the C* law and must be tuned for a specific airframe.

When we go from g-force control to C*, we replace the feedback source of the PID controller with a calculated value C*:
$$ C^* = n_z + \frac{v_{co}}{g} \dot\theta$$
This "fake load factor" C* has the same units (none) as the measured load factor it replaced. It goes into the feedback input of the PID controller. The command input of the PID controller (from the pilot via control stick) remains unchanged.
$n_z$ is the measured load factor, $v_{co}$ is crossover speed in meters per second and $\dot\theta$ is pitch rate in radians per second. $g$ is specific gravity in meters per second squared, as usual. The second part of the formula is basically "what would be the centrifugal force if the aircraft was traveling at crossover speed." We add this value to our fake load factor regardless of actual speed.
The C* law is a compromise between pure g-force control and direct elevator control. If we look at both laws in isolation, we can clearly see the disadvantages that we want to cure:

With direct elevator control, pitch rate is approximately proportional to stick deflection. This feels natural at low speed, but a careless pull on the stick at high speed results in excessive g-forces.

Pure g-force control (through a PID controller) works well at high speed, but at low speed your aircraft will simply not reach high g-forces, period. If you pull on the stick anyway, the PID controller's "whatever it takes" behavior results in excessive elevator deflections and pitch excursions.

C* is mostly g-force control, but with an additional fake feedback term based on pitch rate. From the PID's point of view, the aircraft now always responds to more elevator deflection with more g-forces (fake g-forces at low speed, actual g-forces at high speed), thus ensuring that the "whatever it takes" behavior does not cause problems. The aircraft still pitches more at low speed because actual g-forces are lower, which means overall feedback is lower, which makes the PID controller deflect the elevator harder.

Hi ! Thank you so much for your explanation !
I have tested what you have said in XPlane 12 and yes this works !
But I still have some questions...

Shouldn't the aircraft be more pitrchrate responsive at lower speeds than Vco ?
I read it somewhere that at Vco the pitch-rate and the G-load inputs are equally weighted....G at speeds higher than Vco and pitchrate at lower speeds than Vco...
So how does this approach account for that, or does it ?

Thank you

Awesome !
Thank you so much for the explanation ! :)

By "specific gravity," I assume you mean "the acceleration of gravity?" Specific gravity is usually used to refer to density relative to water.


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Why does Aerodynamic Center move to 50% chord when supersonic?

There are several sources available that state that when an airfoil is fully supersonic, the Aerodynamic Center will move to the 50% chord location. Some of these sources, the ANA shown above being just one of them, use a rhombic airfoil to display how pressures build up after various types of shocks. The rhombic airfoil is simple to analyze and makes intuitive sense why the AC would be at 50% chord.
But what about an airfoil with complex curves, such as the shown Biconvex airfoil? ANA has a table, shown above, that gives a basic overview of airflow behavior as it passes through various types of shocks. Under this explanation, it would seem the biconvex airfoil, with its continuous expansion wave set across both surfaces, would continually speed up airflow and lower static pressure all the way toward the trailing edge, thus causing more lift in the rear of the airfoil than the front.
Specifically, I am curious how all airfoils, when subjected to fully supersonic flow, manage to all have their AC at 50% chord, despite variances in airfoil shape.
Perhaps a distinction between the supersonic affects on center of lift vs center of pressure would be helpful as well.

Just to understand better your doubt: is it clear for you that at supersonic speeds the airflow exactly (more or less) follows the shape of the airfoil? And that this doesn't happen at subsonic speeds?

As long as the contour lines of the airfoil meet at the trailing edge, what happens between leading and trailing edge is inconsequential for lift and only determines lift-independent wave drag (and shock losses from a round leading edge). We cannot explain it better than your literature does already.

Yes the supersonic airflow exactly following the shape of the airfoil is made clear through all basic explanations of supersonic airflow, and that this is different from subsonic. When using the basics of each shock wave type one can easily relate the oblique and expansion waves of a rhomboid airfoil to the relative pressures they create on the surfaces following the shocks. My confusion lies in how to apply this to the continuous curves of the biconvex airfoil. Would the pressure distribution be similar to a rhomboid airfoil except for a smooth gradient between high and low pressures?

Am I to understand that besides for the effect on wave drag, airfoil shape is irrelevant for lift generation, all other variables being equal, during supersonic flight?

Ok, if it's clear that the flow is always perpendicular to the surface then the rest is pure maths. Being the aerodynamic force perpendicular to the surface, being at supersonic speeds the intensity of this force proportional to the local slope of the airfoil and being the airfoil a closed surface then the consequence is that the aerodynamic moment lies always in the middle of the airfoil. Maybe this answer helps you too.

Thank you both for the answers. Sophit’s explanation and link helped a lot. It seems that the generalization that the biconvex airfoil has a lift distribution similar to the rhombic airfoil with the exception that the lift values would change smoothly with the curve of the airfoil is roughly accurate. It also seems that aerodynamically speaking, the ideal supersonic airfoil would be a flat plate, with any other shape not helping supersonic lift any, and only causing more wave drag. I suppose the fins on missiles are an example of this. Thank you both for your time and answers!

I'm glad I could help. I'll elaborate a proper answer then

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How can I find flight history of an old plane with MSN?
I am trying to verify a plane that possibly flew the route between DAC and BKK in the early 80s. It's Thai Airways, DC 10-30,  MSN 46959. It has a pure sentimental value, because a Thai Airways DC 10-30 at DAC is the earliest memory of a beautiful plane I have. I just want to be sure if that's the same plane I remember from my childhood.

Welcome to aviation.stackexchange.com! What exactly do you want to know? Whether the aircraft with MSN 46959 flew for Thai Airways in the early 80's or that it occasionally flew to DAC, or are you looking for confirmation that this aircraft visited DAC at a specific date? BTW, the aircraft has been converted to a restaurant in Accra,

Hi, I just wanted to know if that flew to/from DAC anytime in the 80s. If not that MSN, then which DC-10 THAI AIRLINES did. I went to see off my dad, and saw a DC 10 was being refuelled. All because to validate a memory, to know which exact plane gave me the feeling/dream of being somewhere far away, as if in its presence I felt a call. That's why I am searching that plane.

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How exactly is cruise maintained as fuel is burnt?
Can someone please explain how exactly cruise (I think it’s called straight, level and un-accelerated flight) is maintained for like an airliner please?
I’ve read a few answers on this website for questions in the same ballpark, but none seem to answer my question and are too complicated.
For example:
Do airliners reduce their angle of attack to maintain lift = weight as fuel burns off during cruise?
That Question says: reduce pitch attitude and AOA ever so slowly as weight and lift required is reduced
But how is aoa and pitch changed?

Your confusion isn't clear, are you asking about how trim, or an autopilot works, or how throttles might be reduced to maintain a given airspeed as the plane gets lighter?

Hi, so my question is referring to all of those bits (autopilot, trim,…,)- I dont know what they exactly do to maintain cruise (so the cruise altitude, speed so the plane maintains cruise). To be fair, I don’t even know what trim is and whether it maintains cruise

I’m voting to close this question because it sounds like you're looking for a short tutorial on how flight works. That's a bit broad, though some valiant efforts have been made to address this.

An airplane in level flight can begin to climb by raising its elevator. The air hitting the elevator causes the nose of the plane to rise, presenting more of its wing to oncoming air. This increases its lift and establishes a climb, and also causes its speed to slow.
Similarly, an airplane in level flight can descend by lowering its elevator. This also increases the speed.
As an airplane begins to burn its fuel, it begins to climb. The pilot (or autopilot) can counter this tendency by lowering the elevator a little bit. This will cause the speed to increase slightly, which can be countered by lowering the throttles a bit.

Hi, so I looked online, and it says flaps aren’t really used in cruise? Is that correct? If it’s not, so does that mean that the pilot just adjusts the flap to maintain cruise?

@James The flaps are not usually used in cruise, no. Flaps are parts of the wing that can be deployed to increase lift and drag, but not at cruise speeds. The elevator is a part of the tail which moves up and down to cause the nose to go up or down.

Hello Chris, thank you for clarifying that. So the elevator is used only in cruise? Is it used at all in take offf and land please and, how is it that it can be used safely whilst going so fast in cruise please?

@James The elevator is used in all phases of flight. As the airspeed increases, the elevator is changed by a smaller amount for the same effect. Beyond a certain speed, too large of a deflection of the elevator can have catastrophic effects, so only small deflections are made at cruise speed.

Hi Chris, sorry I’m still a little confused- so why are there the flaps please then on the back end of the wings please? Are they only used in take off and landing phase please? And elevator is universal?

@James Flaps are primarily used for takeoff and landing, yes. I suggest you ask some more basic questions on here or read about the basics. The FAA PHAK and AFH are free and you can find them just by searching on Google. They have a lot of information but are pretty dry. Stick and Rudder is a very good book for learning the basics of how a plane works very well, and a much more entertaining read.

AS the plane burns fuel, it gets lighter, lift exceeds weight, and the plane climbs a little. The autopilot notices the climb, and trims the plane a little nose-down to decrease the AoA and hence the lift. The autopilot thus forces the plane to maintain a constant altitude even though its weight is continuously decreasing during cruise.
The pilot does this manually if there's no autopilot, trimming away lift as the plane gets lighter and lighter.
IN practice, that plane will always get better range the higher it flies, so instead of setting the altitude hold feature in the autopilot, the pilot instead asks ATC for a clearance to higher and higher altitudes as more and more fuel gets burned off during its cruise phase of flight.

Hi, how exactly does trim work please? And how would the pilot do this manually? That’s sort of where my confusion is please?

@James Trim is a way to set where the elevator (or other control surface) will sit if you aren't pulling on the stick (or pushing on the pedals). So rather than needing to pull hard on the stick for the whole flight you can set the trim and then make only small adjustments.

Hi James, thanks for that. I’m gonna read more into trim- it seems like a complicated topic

Oops, sorry I meant hi Chris not James

Well, ”exactly” is a bit broad concept, but the basic idea is rather simple.
Four main forces affect the aircraft in flight. Gravity has to be compensated by lift and drag by engine thrust. When the forces are in balance, straight and level flight is maintained.
The heavier the plane (more fuel), stronger the gravity, so more lift is needed. But increasing the lift also increases drag, thus engine thrust must be increased.
The additional lift required is achieved by pitching up slightly, but in practice the difference is only a fraction of a degree.
So, when the aircraft burns fuel it gets lighter, pitches down, drag decreases and engine thrust is reduced. But the changes in are so minor that any atmospheric disturbance causes much larger corrections so it is very difficult to notice the difference in short term.

Hello, what’s does pitching refer to here please? How is this done?

@James https://en.wikipedia.org/wiki/Aircraft_principal_axes


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Why is only a single underwater robotic submarine Bluefin-21 being deployed in the search for MH370?
As my question states, why is only a single Bluefin-21 being deployed underwater to scan the seabed with an area of around 40 square miles?
Why aren't multiple Bluefin-21's getting deployed when deploying multiple machines would make the search faster when everything here is a very time consuming process?

cost and availability, it is very expensive to deploy the thing

@ratchetfreak I would say only availability. If you deploy 1 for 10 days or 10 for 1 day, the cost remains unchanged

If you deploy 1 for 10 days or 10 for 1 day, the cost remains unchanged very nice point.

@Federico that assumes no other fixed costs, getting the ship supporting ship out there takes fuel and when it is there it can remain there for a few weeks and deploy several days in a row

@ratchetfreak ship fuel is not very expensive though (and now you are assuming that you need one support ship per bluefin)

@fooot we go back to the initial point: 1 AUV per 10 days cost the same as 10 AUVs per 1 day

Would you rather fly 10 AUVs to Australia, then fly them back the next day, or just fly 1 down there and let it stay a while? Shipping isn't cheap.

Bluefin-21

Why not multiple Bluefin-21's

There is only one Bluefin-21.
The other Bluefins 12S, 12D, 9M etc are mostly for shallow water work.
Other AUVs
The Bluefin-21 is not the only commercial Autonomous Underwater Vehicle (AUV) equipped with side-scan sonar.
The US Navy has spent $20M on an order for eight Knifefish (a Bluefin-21 derivative) but these are not due to enter active service until 2017. They are for mine-detection and so (I surmise) may not be well suited to deep-ocean usage.
The Royal Navy has a number of REMUS 600 AUVs but these are not designed for use deeper than 600M
It may be that most existing AUVs equipped with side-scan-sonar are not capable of deep-ocean use.

Judging from the fact that they are replacing dolphins and operating from Littoral Combat Ships, I would say they are not designed for deep-water use.

Most of capable AUVs belong to offshore drilling companies like Chevron and Royal Dutch Shell. Some are also operated by deep sea cable companies.
The various armed forces operate only a handful of these AUVs, and because they are quite expensive, not many marine science institutes have them.

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Icing conditions temperature range: SAT or TAT?
Considering the general rule of thumb defining potential icing conditions: temperature between +10 and -40 degrees C and presence of visible moisture,
is the temperature range regarding TAT (total air temperature) or SAT (static air temperature)?

I've never heard of those.

You can find a good definition in the answer here: https://aviation.stackexchange.com/questions/1640/what-is-the-difference-between-oat-rat-tat-and-sat?rq=1

It would be wise to make it clear your are discussing STRUCTURAL icing and not ENGINE icing. You came close to a -1 when I saw the +10C and -40C :) You may want to reference your source https://www.weather.gov/source/zhu/ZHU_Training_Page/icing_stuff/icing/icing.htm

Thanks @jwzumwalt. In your own reference it says threat exists down to minus 40. Some manufacturers, including Cessna (according to my Citation S2 training at Flightsafety) claim the top end to be plus 10 degrees. This can also be seen here: https://www.aopa.org/news-and-media/all-news/2016/december/pilot/weather-watch-icing-basics. Please elaborate about the difference in conditions between structural and engine potential icing conditions. At the Citation we turn on engine heating at the above conditions, and turn on TKS at the wings+tail when actual icing is encountered.

For the purpose of aircraft limitations, it's TAT for the upper limit of +10C.  SAT for the lower limit of -40C.
Generally once you are going faster (in the RJ, above 230kts) you only need to have cowls on for all visible moisture conditions, and wings only need to be on if actual icing is happening or indicated.  Ice can form on cowls from the temperature drop related to the inlet pressure drop, like carb ice, so the requirements are more conservative for the cowl A/I system.  Cowls are turned on and off way more frequently than wings.

Thinking of this, I believe a pilot should be conservative and take into account both temperatures. Ice can form in places where ram air hits the plane and stops relative to it (there TAT is relevant due to compression), or in places where it keeps on flowing (there its temperature is lower and closer to SAT). Therefore, if SAT or TAT is between +10 and -40 and visible moisture is present, potential icing conditions should be taken into account.
A good explanation of the difference between TAT and SAT: What is the difference between OAT, RAT, TAT, and SAT?


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If I know both Re number and Mach, how do I incorporate both into my simulation?
I’m trying to simulate an aerofoil based on experimental data with flow in the following conditions:
Mach=0.84
Reynolds number (Re) = 3*10^6
I wanted to keep my chord length at 1unit but then what would I use as my free stream flow velocity in my pressure far field boundary condition? Does the Reynolds number even matter here?
Would it be correct to say that the Re doesn’t matter here as I know M=0.8?

This depends on what kind of flow solver you are using and how it is set up.
Mach and Reynolds numbers appear when we write the flow equations in a non-dimensionalized form.  So often, these codes have Mach and Reynolds numbers as direct inputs and the pressure, density, and temperature they work with are in somewhat odd scaled forms.

I’m using a density based solver. I thought that as the Re and Mach cannot be both inputted, but the Mach can be inputted directly into my pressure far field boundary condition, the Re number doesn’t matter?

Are you running in an invsicid mode?  Do you have to turn on viscous terms separately?  If so, I would expect Re to become an option when you turn on the viscous terms.  It also will probably be a 'Reynolds Number per mesh length'.  I.e. If the chord is 1.0, then you could think of it as the Reynolds number at the chord length (at scale).

Hi, I’m running with inviscid assumptions. I’ll look more into what you’re saying, thank you

@SirTimothy  Great.  With inviscid assumptions, Re has no meaning.  Even if you eventually want to run a viscous solution, starting inviscid is often a good idea.  You will be able to get some experience with a case that is easier to set up and that will run faster.

Hi Rob, thanks you for that! Why/when would you run a viscous simulation please?

Whenever viscous effects are important.  If you want to capture the viscous component of the drag.  If you expect there to be flow separation -- either from blunt bodies or stall.  If you are at low Reynolds number and the thick boundary layer will substantially influence the flow.  If you are interested in heat transfer from the body.  Many possible reasons.

Hi, thanks so much rob!


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Where should I start if I want to design a new type of aircraft?
I want to conduct informational interviews with individuals who work in aviation/aerospace to understand the various roles involved in designing a new aircraft and bringing it to market.
I'm curious if I should start with the FAA, perhaps an engineer, or an aircraft designer.

Welcome to Aviation.SE. The question you're asking is an interesting one, and the overview of a good answer to it could cover a chapter or two, with a more complete answer filling a full textbook. That makes it far too broad to be a good fit for the Stack Exchange "Question & Answer" model, which works for questions that can be answered in a post of a few or several paragraphs, rather than chapters. When you have more focused questions about more specific aspects of your project, this may be a good place to get them answered, so please feel free to ask those questions here.

What is the nature of the course? Is associated with business? Finance? Engineering? Are these the aspects that they are considering with that project?

I would think the first place I will start would be what the purpose of this aircraft is going to be, and what kind of a performance profile is required to meet customer needs.

When you say ‘new type of aircraft’ do you mean a new model or a new principle of flight?

You start by setting up a team of people who know how to set up a team of people who can design and build an aircraft.
And yes, that sounds like a troll answer but it isn't. You're not going to do this alone, and you seem to not know who you need to do it so you need to find people who know about such things.


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Does the Osprey ramp have several configurations?
I am building a model of the Osprey.  The kit gives me an option to stow the ramp or cut the ramp in half into two units, the first section lowered and the tail section swing into the top of the aircraft as shown in any photos I have seen.  In those internet photos the ramp is not user friendly for anything on wheels like a fork lift.  My question is does the ramp swing down as one unit providing a beveled leading edge and a less of an incline for wheeled equipment?  I have not seen anything that suggest this except the piece to this model kit.  The end of it is tapered to lie flat on the tarmac.  Even the guys at the museum couldn’t answer this. If so, I plan on modifying the kit to do all configurations.

Does the Osprey ramp have several configurations?

Yes.

Does the ramp swing down as one unit providing a beveled leading edge and a less of an incline for wheeled equipment?

No.  (Not one unit as depicted by the plastic part in the photo...)
The part shown in your photo is actually two parts:
The Osprey, (like the C-130) rear opening consists of a lower "ramp", that is hinged at the rear of the cargo deck and opens downwards and outwards to be level with the deck, or it may be lowered to the ground.  There is also an upper rear "door" that is hinged up by the tail, and is raised upwards and inwards to provide clearance for cargo being loaded via the ramp.
You can see them clearly in the photo here:  V-22 Osprey loading
These two parts are not joined, but can be raised and lowered independently resulting in several different possible configurations.
The model company likely molded them as a single piece for ease of manufacture, as well as ease of assembly for builders who wish to build the model with the rear end closed.  Therefore, to accurately depict what they look like when open on the actual aircraft, the plastic parts would need to be separated.
There is no practical way to join the two pieces and open them as a single unit.  As you can see from the photo, additional ramp extensions are needed for tires to roll from ground level onto the main ramp for smooth loading.

Extensions, of course.  I couldn’t see how it could had been done the way I suggested.  Great answer.  Thanks.

There are multiple images online, showing a 2 part rear hatch. The rearmost part folds up, the rest folds down.
This, from Military.com

https://www.military.com/equipment/mv-22-osprey
The only image I saw of a one piece ramp was another model.

The C-130 has a similar ramp & door. The door can be either up (stowed, as in the photo), or down. The ramp can be either up (which, with the door down, makes for a sealed back end of the aircraft), or level (as in the photo) or down on the ground (ie lower than level, allowing for easy entry of foot traffic or small wheeled vehicles - or not so small in the case of the mighty Herk).

I love that plane.  The ramp is a smooth transition into the cargo bay so that’s what I was looking for in the Osprey. The Osprey, I guess, was designed as a troop carrier and learning of the ramp extensions for the occasional need or using a forklift to the leveled ramp configuration makes much more sense to me.  Thanks guys.

I wish the view from my job was that good.

@Schwern The view comes with the possibility of being shot at.

@Zac67 So does every job in America these days.


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How long can a foreign registry glider stay in the US before having to change the register to N or having to leave the country?
This is a qualification on a previous question, specifically for gliders.
Here is the link to the answer to the more generic question. Juan Jimenez thanks for the answer there.
As other sources suggest different, I wonder whether there is somewhere a explicit mention about gliders or at least an explicit mention that aircraft can stay in the US indefinitely.
I researched Code of Federal Regulations and did not find an explicit mention that foreign registered aircraft may stay in the US indefinitely.
Hence I wonder.
How to be sure?

Do not use GPT for regulations or anything legal-related, it makes up a lot of nonsense.

As far as I can tell, there is no explicit mention of this anywhere. The conclusion that foreign aircraft can remain in the US indefinitely is based on it not being forbidden anywhere, not it being explicitly allowed. Gliders are no different than any other aircraft in this regard.


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Why does the F/A-18 use external aileron and flap hinges?

As seen in the picture, the legacy Hornet uses ailerons and flaps with external hinges, and I was wondering what were the advantages of external hinges compared to flush hinges in the land-based proposal.

Any picture of a super hornet can answer your question. Or do you have something different in mind?

Sorry, my more important question was the pros and cons of each design, but I wasn't sure whether those little bumps really were external hinges or something else.


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Can a tail-sitter drone like the XFY-1 Pogo aircraft have any advantage over a classic quadrocopter
I looked at a few rc models of the xfy-1 pogo plane and wondered why there weren't more drones in this setup, some seemed very agile.  I think this concept can be refined.  of course, the contra-rotating propeller complicates the design, but it is still 1 engine or 2 separate ones with one axis.  I have the impression that I didn't notice any obvious flaw.  I guess that due to wing control there is some delay in vertical flight, so the quadrocopter wins in this respect, but for a very aerodynamic horizontal flight it is a good compromise

They seem to think so on Mars.

Intuitively, less rotors is better because of the reduced tip vortices for the overall rotor disc area.  Contra-rotating rotors tend to balance out torque, which is good, and the lower rotor may result in the downwash being near vertical rather than tending to rotate as is the case with a single rotor.  The main downside is that the lower rotor will be in relatively ’dirty’ air and so will be less efficient.
An advantage of a four-rotor setup is that roll, pitch and yaw can all be achieved just by changing the relative speed of the rotors, so only four moving parts are needed.  This simplifies the manufacture and significantly improves reliability as well as reducing cost.

Thank you for your response.  Don't you think that one engine will still be more energy efficient?  especially in horizontal flight because this system has wings.  additional aileron control is indeed a big disadvantage, although unlike classic airplanes, the control engines can be close to each other, which may facilitate the design

In terms of engine efficiency there’s probably little difference but one large rotor will be more efficient than several smaller ones.  And yes, fixed-wing flight can be much more efficient than helicopters (autogiros being an intriguing middle-ground).  There’s a big difference between small UAVs and manned aircraft in that the size and cost make complex designs less attractive for small craft but much less of a barrier to larger vehicles (variable pitch, retractable undercarriage etc)


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How much knowledge/experience can be transferred between different categories/classes of certification?
This question was originally going to be "Is it possible to earn an ATPL without also ending up with at least one airliner type rating?", but I thought I'd broaden it just a bit (hopefully not too broad).
Requirements for an ATPL in the United States include 1,500 hours total flight time with several minimums in various special conditions and as PIC, "applicable to the aircraft category and class". My question is basically, "what is the definition of 'applicable'?".
For instance, it is theoretically possible, and even useful, to obtain an ATPL in the ASEL class (so the answer to my original question is "yes"; you can earn the FAA's highest certification level without being signed off on anything close to the type of aircraft Southwest or Delta have in their fleet). You could get that license and fly Cessna singles for Ravn Alaska (formerly "Era Alaska" of Discovery Channel fame) or any of the other bush airlines around the country.
However, that represents a lot of flight time before you can even sit the written tests and fly the checkride; 1,500 hours total (250 as PIC), 500 of that XC (100 as PIC), 100 hours night (25 as PIC), and 75 hours real or simulated instrument time (no more than 25 hours in a flight simulator, 50 if you're training under Part 141), all in single-engine fixed-wings. If you then wanted to progress to multis and thus eventually become useful to a major U.S. domestic airline, you would have to start from scratch as a student pilot in the AMEL class.
... Or would you? That's the question; how much of your flight time and/or certification level in one class is "applicable" by FAA regs toward any other class of the same category at the same level of certification? It seems unfair for a pilot with a fairly high ASEL certification to have to start from scratch on flight hours just to fly a plane with floats, or more than one engine, or both. However, they are different classes for a reason; more, or at least different, knowledge and experience is required to taxi a float plane on a lake or to get a multi-engine plane off the flight line. So while there is definitely a lot of overlap between the four "Airplane" classes, it's not 100%.
How about applicability of flight time and certifications to other categories? I'm particularly interested in the "rotorcraft-gyroplane" class and the "powered lift" category, as these were developed as aircraft hybrids which AFAIK have a significant skills overlap with a fixed-wing aircraft. Does flight time in an autogyro count in any capacity towards flight time in a fixed-wing, or vice-versa? How about flying a Harrier? In 50 years when the Osprey makes its way to GA in come capacity, how would existing civilian airplane and/or helicopter pilots get rated to fly it (I hope not by amassing 1,500 hours in an Osprey)? How about something completely different? Even between a fixed-wing and a helicopter there's some overlap (though I'd imagine even the chief pilot of a major airline would be out of his depth in a B204).

The answers to your question lie in 14 CFR 61.159 for airplanes.  Your quoted times for the ATP in the airplane category are correct but some of that time is total time as a pilot, some is just in category and only a small fraction of it is in category and class.
For example, in your hypothetical situation, you have an ATP in ASEL category/class and wanted to add the get the ATP AMEL.  All you need to do (aside from any knowledge tests you may require) is 50 hours in AMEL.  Of the 1500 hrs TT in airplanes, only 50 are required in class.  This is the same to add ASES and AMES ATPs.  You could have a certificate with ASEL,ASES,AMEL and AMES all that ATP level all with only 1500 TT as long as you had at least 50 hours in each class.
The situation for rotorcraft/helicopter is similar and can be found in 14 CFR 61.161.  To get an ATP helicopter, you need 1200 hrs TT but the only hours that need to be in category and class are:

15 hours at night,
200 hours w/75 PIC, and
25 hrs in actual or simulated IMC

You could accomplish all of that within the 200 required hours.  The 200 hours needed in helicopter still count as total time and can be applied toward a fixed wing ATP.
ATP powered-lift requires 250 hours PIC in category with some sub-requirements out of that 250 hours

100 XC powered-lift
25 night powered-lift
75 instrument hours powered-lift

The FAA does not currently issue ATP in rotocraft/gyroplane so you are out of luck there.

If you wanted to min/max optimize the above requirements and get ATP in all of the above the hard category and class requirements boil down to:

50 hrs airplane single-engine land
50 hrs airplane single-engine sea
50 hrs airplane multi-engine land
50 hrs airplane multi-engine sea
200 hrs rotorcraft helicopter

15 hrs at night
75 hrs pilot in command
25 hrs actual or simulated IMC

250 hrs powered lift pilot in command

100 hrs cross country
25 hrs night
75 hrs actual or simulated IMC

At this point you would have:

650 hours TT
325 hours PIC
40 hours night
100 hours cross country
100 hours instrument

Now lets fly 400 hours XC in a single engine (slow and economical) with at least 60 of those hours at night and all of it PIC.
Now we have

1050 TT
725 PIC

400 hrs airplane (at least)
75 rotorcraft helicopter
250 powered-lift

500 XC

400 hrs in airplane
100 hrs in powered lift

100 night

60 hrs in airplane
15 in helicopter
25 in powered-lift

Unless I'm missing something, this is all of the requirements for the ATPs except total time.  Go fly anything for another 150 hours and then take the ATP helicopter checkride.  Then fly another 300 hours in anything and take all of the other ATP checkrides with 1500 TT.

It is also worth pointing out that type ratings and ATPs are different things.  A type rating can be added to a private pilot certificate (though the checkride will be conducted at ATP standards).  You can also earn your ATP in an airplane that doesn't require a type rating (e.g. getting an ATP AMEL in a Piper Seminole).

Good answer. I found that if you are earning your ATPL in the AMEL class, you are required to take a special airliner training course including at least 10 hours simulator time, above all other requirements for an ATPL. The regulation is slightly vague; the title of the section states it's a regulation for someone getting their ATPL "concurrently" with a multi-engine class or type rating (the usual path for an airline pilot), but the language by itself would apply to anyone who would end up with an ATPL-AMEL certificate, even if they already had an ATPL in single-engine classes.

@KeithS Yea, I'm not familiar with the changes there. When I did my ATP AMEL you just needed a normal written (choice of a 121 or 135 written) and a checkride.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Should the aircraft logbook be with the aircraft, or should it be on the ground?
Should an aircraft logbook stay inside of the airplane, or on the ground with maintenance?

This is depending on which country the airplane is registered in, as the requirement to carry the logbook can be implemented per country, e.g. Germany requires the logbook to be carried onboard the airplane.[LuftBO §30 Abs. 5]

In that case, how do they audit the logbook after a crash?

There must be a copy, or something in the ground. But what about the US, they require the logbook onboard?

@abelenky If the original logbook is destroyed, information can also be taken from maintenance logs, older logbooks (need to be kept for 2 years) and other suitable documentation, where hours and cycles can be deducted from.

As an aircraft owner in the US I never kept a logbook in the aircraft.  I do this for two reasons:

Someone from the FAA can come up and ask to the see the logbook when I am on my way someplace.  They can then tie me up for hours while they peruse the logs.  And if they find something they do not like ground the aircraft until we get the issue resolve.  That would strand me at some airport.  If the logbook is at home I can tell them to have their local office make an appointment.
If the log books are in the aircraft they can be stolen when the aircraft is parked.  Since the log books are a history of troubles repaired on the plane, service performed, etc, they are the authoritative history of the plane's health.  As such the log books represent a significant portion of the value of an aircraft (say 10-15%).

I'd daresay that the reason that the aviation agency of the country can request the aircraft logbook is the reason why some countries require it to be carried around. No FAA regulation regarding the logbook?

@SentryRaven Under US regulations you are required to produce the aircraft logbooks if the FAA (or other authorized agency) requests them, but you are not required to carry them in the aircraft.

Out of curiosity, do you carry around a copy of the last page or anything to prove the plane is airworthy, e.g. not exceeding TBO?

@SentryRaven there's no reason to -- the FAA isn't looking to ground an airplane that isn't obviously airworthy with immediacy; they're content to require you to produce the logs in time rather than on the spot. That said, exceeding TBO is not an airworthy issue for all aircraft.

@Sentry Raven - I never carried anything, but I have heard about other owners carrying photocopies of certain pages.  Usually things like completion of an STC (Supplemental Type Certificate) that allowed the aircraft to burn car gas instead of aviation 100LL.

A friend carries an electronic copy of his maintenance log book so that should he need maintenance far from home, the A&P at the remote location can view what has been done in the past.  Just like the pilot's log book, there is no requirement to carry it.  Should you need to show either log to the FAA, producing it in a reasonable amount of time (i.e., go home and bring it to the FSDO next week) is entirely acceptable.

I find this highly suspicious. Were I an inspector I'd ground you on suspicion of irregularities until the logs can be produced...

In the unlikely event that there is an accident that destroys the aircraft, reviewing the logs might help the investigators determine the cause of the crash. And, in the US at least, the insurance company is going to want to see the logbooks to make sure the aircraft is airworthy before they pay out. e.g. If the aircraft is out of annual or has not complied with all of the ADs, my insurance policy states that the company will not cover any damages.

@jwenting, I'm curious, what country do you live in?

@MichaelHall Netherlands.


text:
Is there any ways to earn money from flights with PPL license?
I want to apply a flight school to get flight license (in Thailand), but I have not enough money to pay for CPL training at once.
Is there any legal ways to earn money from flights with PPL in South-East Asia?
Any suggestions are welcome.

Not sure putting your flying on youtube is considered commercial or not. Other than that I doubt Thai CAAT would pursue license action as long as you don’t crash or make other people report you.

Thank you for your opinion. In my case, YouTube blogging isn't the best option, but it could be useful if I couldn't find anything else.

Do you have a skillset that can be used to earn remotely, like software development? Career change is usually more comfortable with the old job for finances. Doubly so for jobs that double as pleasure, so have a lot of beginners competing for the entry level.

It's called a PPL for a reason. PPL is for Private operations only. You may not act as pilot-in-command of an aeroplane for compensation or hire, nor an aircraft carrying passengers or property for compensation or hire. However, you may act as PIC of an aircraft and receive pro rata share, or an equal portion, of the operating expenses (fuel, oil, airport expenditures, and rental fees only) from others onboard the aircraft, as long as you do not pay less than the pro rata share. You can act as pilot-in-command of an aircraft towing a glider, fly for charity, non-profit, or community events, etc.
Edit: This does not apply for all countries, it varies greatly and you must check your laws and proceed with due discretion.

Thank you for explanation.

Note that the exceptions listed may not apply in every country.

Thank you for your remark. Of course, I'll check twice local flight laws before any operations.

Not an answer really, but something you will come up against is the insurance industry's view of your activities. Insurance policies for an aircraft for commercial use are going to entail a very different risk profile, and greater cost, to ones for personal use, and a personal insurance policy for you, a passenger or a client is going to be complicated by a series of legalities that insurance companies will use at every opportunity to refuse paying out a claim. They will not tolerate you making money out of you avoiding paying them.
Be aware of your liabilities in this respect. Things can and do go wrong, particularly to the inexperienced.

I really wonder how this answer is more complete than mine, it literally says "Not an answer". Mine was selected first why did it change?

Tapped wrong button after sleep.

ok sorry if I seemed rude, didn't mean to.

authors: Даниил Галахов


text:
Why are there still fighter pilots in cockpits?
Way back in 2010, Elon Musk said,

The fighter jet era has passed.

And he seems to have a point. Although fully autonomous fighter planes are some way off (see above linked article), why doesn't every existing fighter plane (and, for that matter, recon and bomber aircraft) get retrofitted to allow it to be remote-controlled by a pilot sitting a thousand miles away in a simulator? With a good simulator and good communications, it would seem to allow the same maneuverability, and dynamic decision making capabilities, as being in the cockpit, and remove every pilot from harms way.
What am I missing?
And as a follow up question: Are there any fighter jets flying real missions this way now?

One answer pointed to the QF-16 as demonstrating such tech. It's true they are flown unmanned, but oddly enough they seem to undercut the possibilities that exist. For example, in this account from the Drive:

When flying the QF-16 from the ground under remote control, it’s fairly easy to make mistakes, because you don’t get the feeling of G-forces and you’re not hearing the noises from the jet. The X-ray (remote-control) pilot relies solely on computer screens and instruments. [There’s no live video feed to look at either].

Why on earth wouldn't there be video feeds,  and ground-based simulators, fitted onto such a jet? This does not sound so expensive for the USAF. Even air museums have great fighter jet simulators.
(This video shows some real-time footage from a QF-16 flight, but it looks like they just rigged two GoPros so they could make an ad.)

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That's a great way to make a fighter jet even more fantastically expensive while being less effective.
One obvious problem is latency. 1000 miles is about a 10 millisecond round-trip delay alone even before you add the time it takes to capture and trasmit the wide-angle high-definition images required to replicate what a pilot could see from the cockpit.
Another obvious problem is electronic warfare. A fighter jet with a pilot is difficult to impossible to hack. A remote-controlled fighter jet is possible to hack. You can make this difficult, but keep in mind that you are facing state-level actors, and if they figure out how to hack one jet, they can hack all your jets. That's billions of dollars of jets that are suddenly useless to you, and useful to your enemy.
Hacking aside, jamming is also an issue. An adversary does not have to take over your jet- if they can disrupt communications they can crash your jets.

and, for that matter, recon and bomber aircraft

There are remote-controlled aircraft with these missions. "Fighter jet" is a uniquely bad mission for drones.

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1. Demand
The problem isn't just that fighters are manned. It's also the concept of aircraft designed primarily for air-to-air combat that's getting less relevant.
After Vietnam and Yom Kippur (1970s), wars have seen a decline in symmetrical air-to-air combat. In the Falklands (1982), most Argentinian fighters skipped air-to-air armament. Most of what happened later was interception missions - multirole fighters shooting down light bombers (1990s).
That both last major air wars happened in the 1970s is no coincidence. By 1980, computer tech had enabled surface-to-air missiles to pursue maneuvering targets; SAM kills have been going up and air-to-air going down ever since.
Even when two powers with large, modern air forces clashed recently, they didn't engage in epic air superiority battles. They have set up theater-wide air defenses, killing anything that flies deep inside, and use their aircraft sparingly, close to the frontline. Both do deep strikes on one another, but they use missiles and suicide drones instead of interdiction missions. The odds of coming back from those are too low to invest in reusable aircraft.
Does this mean fighters are dead? Not yet. If two superpowers clash over an island chain, distant enough from either of them, they might not have the same ability to "castle" behind air defenses. It's just that this scenario is a small subset of possibilities, and most fighting happens over land.
2. Substitutes
When one needs to penetrate layered theater air defenses, the loss rate for fighters can get as high as 30-50%. It was such in WWII, it gets back there with S-400 or Patriot present. This means a reusable manned platform isn't perfect for deep penetration.
Drones are harder to spot, flying low and slow. Missiles can fly hypersonic (manned fighters aren't effective there), making them harder to kill. Neither incur PR costs or give the opponent prisoners to interrogate or trade. This advantage is shared by remote-controlled fighters. But the other two - the ability to evade interception, or to easily replace losses - aren't. Fighters are slow to replace not just because of the complexity, but also because they're built to be flown, not stockpiled like missiles.
Stealth is the one counter manned fighters still have to extend their life. But it's not perfect, it's expensive to achieve and maintain, there are counter-stealth technologies and methods. Theater air defenses are being designed to exploit these weaknesses. There's still some cat-and-mouse to be played, but expendable drones and missiles are a safer bet.
3. Complexity
For a remotely piloted combat drone, or UCAV, copying the design of a jet fighter isn't optimal. Fighters pay a lot in weight, fuel consumption, and maintenance costs for supersonic flight, high thrust:weight, and 9g maneuvers, all unnecessary for a drone.
Practical UCAV are built as simple and efficient subsonic stealthy platforms, giving them range without refueling. Starting with the MQ-1, they could carry a fire-and-forget missile for air-to-air. It's not as good as a fighter, but the drones are much cheaper, and with good enough missiles, they can hit bombers or deter fighters.
Converting old fighters to drones can be cheap at first, but their maintenance and overhead aren't. Air wings comprise 30-50 men per fighter, which won't go down much for the same plane, just remotely piloted. That's why QF-16s are used as disposable targets and MQ-1/MQ-9s as reusable combat vehicles, not the other way around. Drones are built for low maintenance.
4. Has it really passed?
Keep in mind that Elon Musk is in the tech business, which does give him a bias for unmanned systems. He builds them, after all. But as spectacular as military tech evolution has been, nothing has replaced "boots on the ground" for the long game yet.
Manned fighters are "eyes in the air". They give the pilot better view of their surroundings, better feel for the aircraft, skin in the game. They'll remain relevant for patrolling non-hostile skies and managing unclear rules of engagement.
But as to how far they'll advance beyond F-35, FC-31 and Su-75 - that's less clear. I expect one more generation for sure. The real question is if there will be another generation of heavy fighters (F-22, J-20, Su-57 successors, with certain risks), or if it will all be light fighters and drone controllers from now on.
Post-Cold War, light fighter programs have been a lot more successful than heavy fighter ones. They provide "eyes in the air" for less, and heavy ordnance can be outsourced to drones now. If I had to guess, I'd expect China to follow up on the J-20, but Russia needs drones more than it needs fighters, and while the US is developing the PCA, it's seeing much less focus than unmanned platforms. India and the EU have been going all-light from the start.
Summary: the role of fighters has been partially replaced by drones, but all major players are still pursuing manned fighter programs, mostly light ones. A human pilot is, with few exceptions, a known quantity; AI systems and remote links are not.

Even at the end of WW2 radar guided flak was getting good.

If I recall correctly, the Falklands war in 1982 saw substantial air-to-air combat. However, the fighting was incredibly lopsided, as the Argentine aircraft (manufactured by the French) were no match for the British aircraft.

@MathKeepsMeBusy True, the island chain scenario. But after the first battle, most Argentinian aircraft didn't even carry air-to-air missiles, they just focused on the ships.

@MathKeepsMeBusy this is NOT intended as a correction - just a comment. The A' Skyhawks did well for themselves in some roles - even though opposed by aircraft notionally their betters.  It doesn't have to be specifically air to air combat for the abilityt of one aircraft to the other to matter.

The USAF already knows how to do this. The QF series of Full Scale Aerial Targets (FSAT). Ex-front line jets, converted to remote control. Key word there - Target.
They've been doing it for decades. Currently, older F-16A, because they ran out of F-4s.
Also, the Predator/Reaper (and others). Remote control.
The reasons that this is not a slam dunk solution for fighters are many.
Latency. The pilot is always just a teeny bit behind what is actually happening. That's just physics. Flying a Predator or Reaper by remote control is fine, because it is just recon, or shooting a slow or stationary target on the ground.
Hackability A person in the cockpit can't be hacked. We've already had an instance of a Predator being spoofed to land/crash somewhere else.
Visibility Instant head and eyeball swivel, in the cockpit, is hard to recreate with cameras.
Long lead time The current F-22 and F-35 have been in development for decades. Long before real remote control for actual fighter jet capabilities would have been an option.
Remote control for a Reaper mission is much different than what is needed in direct air to air combat.
The new B-21 Raider bomber is supposedly going to be "pilot optional". Again, the flight profile for a bomber is quite different than air to air.
Anecdotally, I have heard rumors that the USAF is investigating the QF-16 concept for actual combat.
Bottom line answer to: "Why are there still fighter pilots in cockpits?"
Because the technology and trust has not yet evolved enough for a full solution. The 'trust' is actually trusting your national security to this still evolving tech.

"Latency"  If latency is important, then how to anti-air missiles work without a pilot?

@AnonymousPhysicist, I think those are autonomous.

@AnonymousPhysicist: Missiles have an onboard sensor, and have a very simple goal: fly toward something that's significantly slower than they are.  This was possible with 1950s era analogue electronics with a feedback loop between control surfaces and the seeker/sensor head: https://en.wikipedia.org/wiki/AIM-9_Sidewinder#Guidance .  (Other missile types might have their own radar emitter for fire-and-forget homing via radar instead of IR (Fox 3), or just detect radar reflections from firing plane's radar (Fox 1). Still the same aiming task.)

@AnonymousPhysicist: So anti-air missiles have basically zero-latency for finding the angle / bearing to target, thanks to an onboard sensor which they use at least for the final attack phase, if not the entire flight for more sophisticated missiles(?).  I assume ground-fired missiles are the same in that respect.

@PeterCordes That's correct.  So why would an unmanned fighter jet be different, particularly when attacking?

@AnonymousPhysicist: Because it's probably not hugely faster and more maneuverable than the enemy plane, so it needs to be clever and set up a maneuver which will bring it into attack position, not necessarily just try to point the nose at the enemy.  Also, we're not trying to collide with them.  But yes, you could plausibly have enough onboard AI to make dogfighting decisions with the remote operator being more of a target-selector than a full pilot for the final attack phase of a fight.  If it ever got to guns range anyway; good long range missiles make that much less likely.

@AnonymousPhysicist - a missile is mostly autonomous. Fire and forget. There is no control loop from ground to satellite to missile to satellite to ground.

@AnonymousPhysicist Pilot's main job is to make decision "should I engage". Missile starts operation after the decision making has been finished.

Suggestion for new bulletpoint: visibility/stealth. A transmission going in and out of the plane is yet another way how the enemy can detect you.

@WPNSGuy True.  Now why would the unmanned aircraft need ground control with low latency when attacking, while missiles attack without that?

An unmanned aircraft might need low latency when landing in gusty conditions.  That's readily solved by putting the pilot and his transmitter on the ground next to the runway.

@AnonymousPhysicist I'm going to argue that if you have trouble automating landings then you aren't at the point of flying automated mission profiles.

@AnonymousPhysicist - Because missiles and fighter jets do completely different things.

Just a small minor correction.... Almost all missiles use some variation of what is called *proportional navigation" https://en.m.wikipedia.org/wiki/Proportional_navigation#:~:text=Proportional%20navigation%20(also%20known%20as,direction%20as%20the%20range%20closes.

@PeterCordes, the article about the sidewinder includes many misstatements. The sidewinder (like almost all missiles), uses what is called proportional navigation). The only data used is line of sight, (LOS) rate. The rate of turn of an imaginary line between the missile and the target. If the LOS is constant, (it is not turning or rotating), the missile is on the collision course, (*for the current missile and Target flight paths/velocities).

Of course if either the target or the missile changes flight paths, then the LOS rate will change. The missile seeker head dies two things. Furst it keeps itself (the seeker head) tracking, (pointed at), the target, and 2, it has a gyroscope mounted on it to measure the LOS rate of the seeker head. Then, that LOS rate is fed to the guidance computer which makes the missile turn in the same direction as the LOS is turning, at a rate that is proportional to how fast the seeker head is turning. That puts the missile back on the collision course.

Indeed, this where the Sidewinder missile got its name. When it first comes off the rail, it is slow, and needs a lot of lead to get to the collision course. As it accelerates, it needs less and less lead,  the LOS starts to move back towards the target, and it turns back towards the targets nose. Then when the motor burns out, (~6 secs), it begins to slow down, and needs more lead again. From the shooters perspective it looks exactly like the path of a rattlesnake across the ground.

Of course, for modern missiles, with higher launch range capabilities, the above only describes how the missile maneuvers in the terminal end-game intercept portion of missile flight. During initial launch and cruise phases more complex algorithms are utilized to take advantage of thinner air & higher cruise speeds that are possible at higher altitudes.

Put simply: Elon Musk is a big bag of wind.
On a more serious note, he’s done a number of good things in been involved with a number of projects, but his ability to predict the future with new technologies has more misses than hits.  One need only reference the Boring Company, hyperloop, Neuralink, Twitter (now X) takeover, the Tesla solar roof, Tesla electric semi truck, supersonic VTOL electric jet, and still failed Starship and ludicrous plans to colonize Mars due two years ago for this.  You need to understand something about Musk.  His fortune is planted in Tesla as well as SpaceX stock.  If those fail, he’s going to be near broke.  To make money, therefore, the name of the game is to continue to get the stock prices of those companies jacked higher and higher.  To do this, Musk is banking on his genius public persona to support his own flights of speculation and bombast.  So far, the media, as well as Elon’s legions of devoted fans have indulged him in this game.  But sooner or later, that kind of behavior will be a kite that will inevitably land in the mud.
Now, in regards to a fully autonomous AI driven fighter aircraft,  we’re not quite there yet in the technology sense, though a number of defense companies like Anduril are pursuing this.  Just when we arrive at the point where a fully autonomous fighter is practical as well as accepted by the military is anybody’s guess. Some reports are giving it no more than 20 years away.  Artificial intelligence is nowhere near capable of innovative and pure creative thinking for tactics and can only stochastically parrot what it has been taught.  It’s still unclear as to how AI and fully autonomous aircraft will handle challenges, everything from changes and mission parameters, rules of engagement to emergency procedures.  A lot of the stuff represents the great unknown and currently no known AI is capable of coping with it.
“Even ‘Star Wars’ had a pilot in the cockpit.  Air combat is so dynamic, the human element brings flexibility that I think will actually be the key to success out there.  Because there’s just no substitute for being there, on the spot, in the air, seeing who’s injured, who’s not damaged, who’s in trouble, who’s not in trouble.  There’s all sorts of things that the pilot can do at the scene that someone, far away from the scene or remotely flying it or a computer controlled airplane will never, ever be able to figure out.”
- Cmdr C.J. ‘Heater’ Heatly, USN (Ret.)

Star Wars had pilots in the cockpit because it has human actors carrying the story. Those droids are more than capable. Indeed, they are too capable and are hamstrung so that they don't pose too great a danger.

Elon Musk has a public persona that is wacky at best, alarming at worst. And he's full of hyperbole, including Mars. But a startup company founded twenty years ago is now the world's leading space launch provider, with other countries now trying to copy some of their methods. SpaceX also launched the first Americans to orbit from U.S. soil in over ten years, while aerospace giant Boeing struggles to do the same. The accomplishments of SpaceX and Tesla are astounding, so it's understandable that he has many fans. Starship is the most ambitious rocket ever attempted and is making rapid progress.

All fine points but a stooped clock is right at least twice a day as well.

That's an irrational comment if you think that it was just dumb luck that SpaceX has made over 290 successful launches to orbit with only one failure, including ten crewed flights and nine ISS cargo resupply flights. And no other company or even country has recovered and reused a first stage booster, SpaceX has done it over 250 times. Again, wacky, alarming, and hyperbole. You will sound rational if you criticize that about Musk, but not when claiming Musk is a failure.

It’s also irrational to say that because Elon ran a firm which did that, therefore he’s an authority on subjects like modern warfare - specific on whether manned jet fighters should continue to be a part of the DoD’s armamentarium.  What I am pointing out is that Elon makes a lot of predictions that do not come true because he doesn’t know what he’s talking about, and this can be proved out using very basic back of the envelope calculations.

I will also add that in the successes that Elon has had in his career, they have an essence been either 1) hostile takeovers of firms on the technology forefront (Tesla) 2) developing already existing products (Tesla, SpaceX), 3) or been discharged for incompetence after creating a company that went on to be successful when not under his leadership (PayPal).  Again, Mr. Musk’s business model has been hype, and using these disingenuous claims of success to get people to invest on his crazy ideas and boost his stock holdings, not in the development of tangible hardware.

Musk is a great example of why brilliant, mercurial masters shouldn't be let too close to direct social media.  While their brains spout out incredibly good ideas, they also spout out a much larger volume of incredibly bad ideas.  Given sufficient time, the turds will self-extinguish, while a great idea is "asserting itself with ever-growing insistency" as Daniel H. Burnham puts it.  This is why social media reduces geniuses to hated twits - the countless bad ideas get airtime far too hastily.

Romeo_4808N - I fully agree he's not an authority on everything, that's what I meant by wacky, hyperbole, etc. Even what Musk says about space is often over the top. I routinely clash with SpaceX fans by saying that Musk's claims of launching a fleet of 100 Starships to Mars with 10,000 people on board is nothing but hot air, even if Starship itself has great potential. But the achievement of literally taking over the global space launch industry, and creating a successful car company is evidence of tremendous innovation. I think your description of how he became successful is a bit shallow.

FWIW, this is not an unusual assessment of Elon's ideas. Take a look through his bio, and one thing that jumps out at you is that every time he financially "leveled up", it was after the people running the business he invested in ignored his ideas, and went with something completely different that hit it big.

Elon single handedly: rapidly accelerated the transition to electric vehicles, scaled the biggest rocket launch platform in the history of humanity and built up the world's first high-speed satellite internet network. Neuralink hasn't failed yet, Starship hasn't failed yet, Twitter/X is still growing or at least stable in popularity (just look at how Biden primarily used X to announce his retirement from running in the campaign), Tesla semi truck hasn't been released yet. So -1 for misinformation and a clear political bias.

@Romeo_4808N wrong, he took over Tesla when it was a tiny company 10,000x smaller than today, ditto for SpaceX. PayPal wasn't his solo venture but he contributed a lot to it. Your statements are pure cope from people who keep seeing massive Elon successes (such as the insane success of his rocket launch platform) and then try to find an excuse as to why he doesn't deserve credit.

All interesting points.  However the proof on my listed projects is in their progress.  And they are sadly lacking there.

I don't think you've established that 'keeping pilots out of harms way' solves a problem that needs solving. Most modern fighter aircraft losses have been outside of combat, and the pilot has survived via ejecting.
The US military do not want to lose fighter jets, whether they're piloted or not, because they're extremely expensive, and slow to replace.  A conventional modern fighter jet costs over 100 million dollars.  Making them 'remote control' will probably increase the cost dramatically, so losing them in combat will become even less desirable.
That the pilot (with a training cost of circa 10 million) may or may not survive is pretty much a secondary consideration, when you look at the hard maths of war.  There is an excess of trained fighter pilots, and no shortage of people wanting to transfer to a front-line fast jet squadrons.

Extremely interesting point.

Are military drones and their munitions subject to the same air worthiness standards as manned aircraft and their munitions?

The pilot is flying an old design.
Elon Musk said that in 2010.  The F-35 program started around 1997 and became operational around 2012.  The J-20 program started around 2008 and became operational around 2018.  These programs might last 50 years, keeping pilots in the sky for quite a while.
If you wrongly assume retrofits are better than building a new plane, it would take 10-15 years to develop the retrofit and it would be kept secret.  If you think that procurement officials agreed with Musk in 2010 and started retrofitting procurement in 2010, then check back in 2025 to see if they succeeded.

Are there any fighter jets actually flying this way now?

If by "fighter jet" you mean "anti-air weapon," then yes.  The Patriot has been operational since 1984 and, once launched, is autonomous.  The S-300 ha been operational since 1978.  These unmanned weapons are not jets and are not reusable.  In some situations, those features make them better than fighter jets.

Very good point about Patriot.  If I'm going to make a flying weapons platform that can fire missiles onto targets,  why not just fire the missile from the ground.

A very good 8K video display provides only 33.18 megapixel resolution when the "native resolution" of the human eye is commonly cited as 576 Mp. Not all this information is processed by human brain, but the brain and already the eye itself are both very good in selecting what is important and what is not. Right the same cells that capture the light in retina are also the neural cells and start signal processing immediately. The eye instantly turns itself to place the object of interest into the center of retina, where the resolution is much higher.
And the data transfer rate of this good monitor is 80 gigabytes per second. It can be compressed to be much less, but the latency will soon be enough to make the difference.
This difference will likely put a remote pilot into inferior position, constantly claiming that the camera of the drone never points into the right direction on time. It may be cases where it matters less, but as long as the outcome of the combat depends on ability to see and aim at the enemy first, the remote pilot does not have many chances.
One of my tasks was to observe experimental robots with remote camera, with the goal of stopping them in time if they do something wrong. While the task was easy to manage when watching the robots directly with finger on the button (reaction time of 200 ms or about), with camera never showing the center of the problem properly and all latency added, it was totally mission impossible.

The answer is that this is being investigated. Check out Red 6, and what they are doing. Initially, they are investigating the concept to see if it might be a way to train new fighter pilots using a virtual adversary, but it's not a great leap to put the pilot in a cockpit on the ground, connected to the airframe over datalink...  It may or may not pan out. There are many issues associated with it, but it takes time,  (and money), to research and investigate all of them. Jets cost a lot of money and it would be stupid to build a fleet of them before we are confident in the concept.

Because all the sensors in the world are trickable by electronic jamming.
Organic eyes and reflex are immune to electromagnetic interference.
More point Once digital doodads are hacked with Virus, malware, corrupt code, false sensor readings the robots will fail.

As others have noted with remote control, the signal can easily be jammed and worse, spoofed. imagine your enemy suddenly taking control of your armed drones and attaching you.
The signals the drone has to send back to you also provide a beacon that can be used to track the drone.
Most of these are not major issue when attaching a low tech opponent, although it is not wise to under estimate your opponent.
You could make the drone autonomous instead of using remote control, but no is quite ready to take humans out of loop when using weapons.


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Are Hybrid-Electric Propulsion Systems the only avenue to achieve the range and speed equivalent to current airliners?
Airliners like the A320neo and 737-800 use HBP Turbofan engines to achieve cruise speeds of around 0.8 mach, and have ranges around 6,300 km. Therefore, is the only means of achieving similar numbers with more-electric focused propulsion to still utilize the HBP engines that are currently in use with electric supplementation? Or are there avenues that would no longer require combusting traditional jet fuels?

I do not believe that All-Electric or Hybrid-Electric will ever compete head-to-head with traditional jet-fueled HBP engines. Rather, electric flight will fill a different niche, enabling smaller regional flights, probably with slower, lower flight, at a price-point impossible with modern jets.

This looks like an opinion-based question because it can only be answered with large doses of speculation about heretofore undeveloped technologies.

The two big problems that electric propulsion has to solve are 1) energy density and 2) the fact that as fuel burns off, the airplane gets lighter and more efficient. 1) can be solved with some super-speculative "magic" future battery technology. 2) will never happen for batteries, so they need to be significantly more efficient than combustion engines to even just break even.

"Or are there avenues that would no longer require combusting traditional jet fuels?" – That question hints at the direction the industry is currently going: the trend is not towards electrical propulsion, but instead to combusting non-traditional jet fuels.

@JörgWMittag So something like redesigned propulsion systems that burn SAFs or hydrogen fuel could be the key towards reaching the performance we see today?

The “alternate energy propulsion system”, that might one day replace the current airliner propulsion, has yet to be invented. I think you need t look FAR outside the box for any possible replacement.

We need a crystal ball, or we can answer with opinion, which are not allowed on this site (as design)

The premise of this question - that hybrid systems can compete with jet fuel on range in the first place - is unproven and likely incorrect.
I would however direct anyone interested in understanding the why to a few articles by Bjorn Ferhm, a commercial aviation analyst, who crunched the hard numbers.

Hybrids, also simplified
Serial hybrids, also pt.1
Parallel hybrids, also pt.1

The short conclusion is that:

Batteries don't hold enough charge for long-range flight, and
There's no opportunity for regenerative braking in flight to make hybrids useful.

Electric propulsion can be useful at short range. It's perfect for training or for pleasure flights. Adding a range extender wrecks the simplicity and economy of an all-electric aircraft.
There are avenues for long-range flight that no longer require combusting traditional jet fuels. These are hydrogen and SAF (sustainable aviation fuel). Both work by burning fuel in a normal turbine engine.

I deeply deeply appreciate your answer! I also apologize for the question being a bit of a non-comparison. I supposed what I should have asked was something more akin to my last point of "without burning traditional fuels," which you aptly pinpointed at the end of your answer. So, thank you again for the info! I will be sure to take a look into the links you sent.


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Will air traffic control ever ask a plane to not brake hard on a landing?
In another question, somebody asked why an airplane might not deploy thrust reversers on a landing. One of the answers suggested a few options, including:

Depending where the gate was, they may simply have wanted use more of the runway to speed up the taxi

It occurred to me that it's not just a matter of a pilot wanting to get to the gate sooner; it could be that ground control wants them to take that last exit (for whatever reason), but air traffic control wants them off the runway quickly so that they can use it for another airplane.
I assume the final decision of how to conduct the landing is the pilot's. But will air traffic control ever ask nicely, "you're going to be taking the last exit, but please don't do the final bit of braking until the end, because we'd like to get another flight taking off right after you land"?

Related

Funny- my first reaction was: icy runway, so do everything carefully

At least in my experience, ATC won't ask for specific levels of braking, they'll ask you to exit at a certain taxiway, hold short of an intersection, &c.  How that request is accomplished (and whether it can be) is up to the pilot.

Yes, we can ask you to plan your landing roll in a certain way. We won't technically instruct you to brake the aircraft in a specific way, but simply to aim for a specific taxiway after landing.
There can be different reasons for this, but generally it is an attempt to expedite traffic flow on the ground at the airport. For example, if you are landing on a long runway and your parking position is near the far end of the runway, I might ask you to keep the plane rolling down the runway and vacate at the end, in order for you to have a shorter taxi time.
It could also be that the taxiway you would normally use to leave the runway is blocked by another aircraft or vehicle, and I want you to leave the runway via a taxiway that is further down the runway.
However, extending the landing roll does extend the runway occupancy time as well, so if there is another aircraft behind you on short final I will not offer you to perform a long landing roll. This is also why you should always ask ATC if you are planning to perform a long landing for one reason or the other – if we have someone else just a couple miles behind you, we might have to instruct them to go around if you do not vacate the runway like we expect you to.
With regards to reverse thrust specifically, there are airports where the use of reverse thrust is only permitted in special situations. This is to reduce the noise level at and around the airport. However, this is purely a regulatory thing, and is not actually related to ATC.
ICAO offers the following guidance on  the subject (DOC 4444):

7.10.3.1    When necessary or desirable in order to expedite traffic, a landing aircraft may be requested to:
a) hold short of an intersecting runway after landing;
b) land beyond the touchdown zone of the runway;
c) vacate the runway at a specified exit taxiway;
d) expedite vacating the runway.
7.10.3.2    In requesting a landing aircraft to perform a specific landing and/or roll-out manoeuvre, the type of aircraft, runway length, location of exit taxiways, reported braking action on runway and taxiway, and prevailing meteorological conditions shall be considered. A HEAVY aircraft shall not be requested to land beyond the touchdown zone of a runway.

Situations vary, but more than once I have been asked to:
"Extend rollout to the end of the runway"
"Land long on the runway"
"Will you accept a landing after the half-way point on Runway 4, 6,000 feet remaining?"
Addendum #1
Heard yesterday, the tower telling a bizjet, while on 2 mi final, "123MA, cleared to land 27, taxi to end of the runway for left turn at Alpha."

@757toga Actually, ATC can instruct aircraft to land beyond the touchdown zone (not heavy aircraft, though). See my answer for details.

@Johnny "b) land beyond the touchdown zone of the runway; " directly from J.Hougaards answer

All the land long instructions I have gotten from ATC have been in the form of "will you accept", with the exception of places already NOTAMed for landing long, like at the OSH airshow.  Separately, I did not get the impression that this question was asked only in terms of air carrier ops.

The verbiage I usually get when ATC is interested in expediting our landing rollout is "long landing approved". This is not an instruction, and is not given as such. The runway is ours to do with as we like, but we would also like to expedite our arrival at our parking spot.

authors: Vladimir F Героям слава


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What causes the distinct sounds of a jet engine?
I live a few miles from a major airport (BOS), under the path that a lot of airplanes use to depart. The planes are somewhat low over my house -- high enough that it's not deafening, but low enough that I can make out the livery. Judging from a couple planes I just looked at on flightaware.com, I'd guess somewhere in the 5,000 - 8,000 foot range.
I can often make out three fairly distinct sounds from the planes:

a mid-range roar, the sort that one would typically associate with a jet flying overhead
a sort of whistling
sometimes a buzz

The buzz isn't always there, but when it is, it's quite loud; significantly more noticeable than the other two.
What causes each of these sounds? I know there are different components of an engine (I'm guessing the main ones for this question would be the fan, compressors, combustion chamber, and turbines, and possibly the nozzle). I'm guessing each contributes to some, but not all, of the sounds.
If it matters, my house is around where the planes turn (they often take off heading more or less NW, and then turn west or SW where I can see them). I think the buzzing (when I can hear it) is loudest when the plane is at about a 45 degree angle to me (so I'm seeing its front-left as it's climbing), but I wouldn't swear to it.

An airframe alone contributes a surprising amount to an aircraft's noise.  When an aircraft is gliding much of what's heard is not from the engine.

@STWilson Hm, interesting. That could be I've of the sounds. The Wikipedia article on the Gimli glider suggests it's not much noise, though: "Complicating matters was the fact that with all of its engines out, the plane made virtually no noise during its approach. People on the ground thus had no warning of the impromptu landing and little time to flee."

As I think about it, the noise from the engines radiates in all directions as it's being generated internally and "pushed" out. The wind noise from the fuselage cutting through the still-ish air (Gimli Glider) is mostly being left in the wake of the plane as it's passively generated, thus the GG's noise wasn't a warning for those in front of the plane. IANAAE I am not an audio engineer...

Related: this (very similar), this

There are several dimensions to the answer on this topic.  First, consider that different flight profiles (TO, approach power, final approach power, etc) will have different engine acoustic signatures.  The sound output from a jet or turbofan is not linear with power, rather it changes with power level, and resulting flows and RPMs. Second, consider that the polar acoustic radiation is different for the aircraft. Nose down vs nose up, banked, etc. and consider that these radiation patterns are changing with respect to power. These are the primary noise factors.
Secondary noise factors include APU operation, and airframe noise. The airframe noise is greatest with airspeed which impacts boundary turbulence energy, and then with gear extension, and flap/slat/spoiler extension and slips.
To this complexity add airspeed, and aircraft configuration.
Different engines have decidedly different spectral content, and some are quite characteristic.
The bulk of the engine noise is exhaust turbulence, and quite specifically the differential of the exhaust velocity and the ambient flow.  This is why turbofan engines are much more quiet, because they have a more gradual gradient between the ambient flow, and the jet flow.
Whines are often forward directed radiation and are largely acoustics from the intake, and most specifically from fans on turbofan engines.
There is a plethora of literature on A320 engine whine and solutions with different engines.
There are also some specific airframe noises.  For example, the same aircraft, the A320 has some open vents on the lower wings, and the addition of vortex generators has been shown to reduce this noise substantially (up to 11db, which would be perceived as half the noise, and is a more than 99% acoustic energy reduction.  Some A320 aircraft can be heard from 30 miles away.
To address your questions, the roar is mostly engine noise.  The whine is also engine noise, but can sometimes, on some aircraft be port or acoustic flutter noise.  The buzz noise is normally airframe or to a much lesser degree airframe and engine interactions.
Apart from civil aviation there has been a lot of work done, and thousands of papers written on acoustic signatures of aircraft. There are various sensors equipped with correlation software which will classify aircraft in the air, from the ground. Aerospace contractors work hard to reduce the signatures of every aircraft from large transport to fighters. Civil aviation responds to different threats, which are the public complaining about noise associated with airports near cities.

As I commented above, the buzz seems too loud to be from the airframe alone. Do you have any citation for that? I may have mis-described the sound; I looked up a video, and it's the buzz that's at 2:03 here. Seems to be coming from the engine.

Inlet fan shockwaves is my guess.  Flying with my buddy who flies A320 later this week and can ask him.

Ah, that makes sense!

Talked with him briefly on phone, and he suggested you might look at a320whine.com.  Not the noise mentioned above, rather the FOPP, but you might find it interesting.

Huh, that whine does sound similar to the whistling noise I meant! And it'd make sense, since I don't think that's on every plane either, now that I think of it. That page only mentions it happening on arrival, but there's no reason it wouldn't also happen shortly after takeoff, right?

Let me ask the A320 captain.  I think the flow over the cavity is different with a TO configuration.


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When a typical commercial airliner flies overhead, what is the actual noise we are hearing?
We're all familiar of the sound planes flying quite high overhead and you hear a faint drone, even when planes are lower to the ground you hear them scream at a slightly higher pitch, but what exactly are you hearing?
I would guess it's either the sound of the fan blades spinning extremely fast or the noise of the air (thrust) being forced out the rear of the engine?

Related: What causes the distinct sounds of a jet engine?

also related: What makes the swooping noise when a jet flies overhead?

It depends on the type of operation:
Approach (close to airport):

Much aerodynamic broadband noise from the air-frame
Modern turbofan engines are less noisy than the air frame during approach. But engines emit most of the tonal components in the sound.
Depending on the type of aircraft and angle of descent the pilot might need to use air-brakes to reduce speed. That will cause turbulence and noise.
On some Airbuses you hear a typical high pitch annoying sound that is caused by air flowing across cavities under the wing (Fuel Over Pressure Protector to be exact, not from the engine).

Departure (close to airport):

Pretty much all the noise you hear comes from the engines, such as the buzzsaw noise generated when the tips of the fan blades reach supersonic speeds. Hot high speed gases causes turbulence and that creates low frequency noise, especially behind the aircraft.

Overflight at 35.000-40.000 ft:

What you hear is low-frequency broad band noise that originates from turbulence behind the engines. All the high and medium frequencies are gone because the air between aircraft and ground absorbs much of the sound. The sound will also fluctuate due to differences in wind speed, humidity and temperature, along with the flight path and along the sound propagation path.

Further reading / sources
1. Conference lecture by Prof. Dr. Ing. J. Delfs,
Head of Technical Acoustics, German Aerospace Center
2. ECAC doc 29 (Technical documentation)
3. An Overview of Aircraft Noise
Reduction Technologies

On the approach, might a lot of the noise comes from the flaps (part of the airframe bit you mentioned, but if you're going to call out the air brakes specifically, then flaps might be fair game, too). At least when I'm on the plane, there is a significant increase in volume once the flaps are extended, even to the first position.

Wow that's amazing, while it definitely was a thought, I really didn't expect that air flowing around the aircraft or its brakes could generate such loud noises.

@Ksery: You would understand the airframe noise if you've flown light planes, or even (maybe especially) sailplanes.

The main improvement that could be done to this answer is to provide sources so that this is no longer your personal opinion.

@CGCampbell - That could be done! What is the appropriate way? Edit the answer or provide them in the comment section?

The question is best.

Here's NASA Glenn's breakdown of the noise emitted by a typical commercial airliner with 1992-level technology.

Image source

This could be improved by explaining the different items, and also citing the image source.

Your graph indicates that approaches makes more noise then take offs. That is not true and I think we all agree on that. Could you have missunderstood the graph? I would guess that what is shown here is sound pressure level at a location closer to the approach path then the take off path?

Also, how old is the chart and what was the "typical commercial airliner" that it is based on?

@Sports Racer : Clearly the chart is wrong. There are no engines that emits less noise during take off.

There are many great YouTube videos on aircraft noise reduction such as this NASA noise reduction program

It won't surprise anyone, the majority of noise during takeoff is the engines.
What is interesting is the engines are now quite enough that during landing, most of the noise comes from the wheels and flaps whistling and rumbling!


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If the pilot cabin loses pressure, can the pressure difference lock the cockpit door?
I think, if there is only a 0.1 bar pressure difference with a single square meter door, around the weight of a ton would be needed to open it - if it is sealed hermetically and opens outward.
Is it possible?

If you're thinking about the Germanwings crash, note that according to the AvHerald article, the CVR heard the first officer breathing normally during the entire descent.

Can the pressure equalize thru ECS (page 11)?

@HenningMakholm Ok, it will be my next question - human breath is normally silent, especially with the backgroound noice of a plane.

@HenningMakholm Sorry for the late reaction - but, depressurization doesn't cause shortness of breath. It is caused by the increased $CO_2$ concentration in the blood. In the case of depressurization, this decreases. I once talked with a pilot, he said they were trained for that. As he said, he didn't feel any asphyxication, he feels himself normal - except that he starts to feel his body extremely weighty. And they lose consciousness very quickly, there is no willpower what could it compensate. And he breathes normally.

Firstly: Flightdeck doors are to the best of my knowledge not hermetically sealed.
Secondly: Doors will normally have one of several solutions employed to safely handle explosive decompression:

Some doors have panels that pop out to equalise the pressure, especially inwards.
Some doors unlock automatically in one or both directions.

Needless to say, you need one solution in either direction. Whatever pressure difference there is it will most probably very quickly be equalised and there should not be any difficulty in opening the door if need be.


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I would like to know where ideally it is to be sat on an Emirates A380 to get a nice picture of the wing and wingtip as well as the outer landscape?
I would like to know where ideally it is to be sat on an Emirates A380 to get a nice picture of the wing and wingtip as well as the outer landscape?
LHR-DXB 7:50 P.M

The seats in the back. This question does not really seem to be on-topic here though.

Ideal place to sit would be a window seat back of wings

Sitting in the back means that the landscape below is blurred by the density differences between the hot engine exhaust and the surrounding air. Sit in the upper deck and look for a seat near the leading edge on SeatGuru.com.

Emirates operates a B777 on that route. Pick a different departure time for an A380. 4:55 or 8:40 pm get you on an A380.

The best seats would probably be in the back because you can see the wing and the ground without having to twist or having the wing in your view.
Here is a picture I took from the back end of a Boeing 757-200. Is it the view that you want?


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What happens to en route flights when a major earthquake etc. destroys facilities?
Suppose you're flying a big plane in to an airport like Mexico City, already in final descent, when an earthquake strikes.  Large cracks appear in the paved infrastructure catching some vehicles by surprise.  The airport suspends operations.  Planes planning to take off are stuck on the tarmac for at least several hours.
Planes planning to come in from farther away are told not to, maybe from an external seismic monitoring service if communications are out.  Those already in the air but far enough away to be able to divert can land at other airports.
Yesterday, the main infrastructure was inspected and found to be OK, and the airport reopened several hours later.  But what would have happened if the earthquake had been strong enough to destroy the runway or other landing-critical infrastructure at this airport and at the nearest alternative, so that neither "rack & stack holding patterns" nor "just go to the alternate" (as in e.g. a terrorist takeover at one airport) are viable options?  Are there special rules/considerations in place to help protect safety in such a rare region-affecting event?
Continuing the distinguishing analogy from the terrorist takeover question, this situation is more like a widespread cyber-attack, solar flare, or electromagnetic pulse that knocks out ground facilities and prevents landing at multiple airports without destroying in-air flights in a way that e.g. a sudden volcanic eruption or nuclear explosion might. This question also focuses on emergencies that arise quickly and without the kind of notice that would permit a planned closure (as e.g. a hurricane would).

Related

Well, suppose that some alien-generated catastrophe destroys all airports and ATC centers in the world. What would the pilots do? They'd try to find a piece of highway without wires going over it to land on. In more normal circumstances they will talk to ATC and try to figure out if there are any alternates that are still open and divert to there.


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Simulating a tip vortex
I have read on this forum that the tip vortex comes from the roll-up of the vortex sheet behind the entire wing as opposed to being a local tip phenomena.
I am interested in simulating a tip vortex numerically. Does this mean I am obliged to model the entire wing?
But this makes the simulation much more expensive! Is there a way in which it makes sense to only run CFD for the near-tip region for accurate results? For example a boundary condition to replace the rest of the wing? Any discussion or papers are appreciated.
Many thanks

The cost of a simulation depends not only on the size of the domain, but also on the modeling strategy, the desired outcome, the acceptable error in the solution.
Are you using RANS, URANS, LES or DNS? Which grid size? What is the purpose of tour simulation: fluid-structure interaction, aeroacustics, wake interaction, ...? You might end up with a full-wing simulation that's not so expensive

I have read on this forum that the tip vortex comes from the roll-up of the vortex sheet behind the entire wing as opposed to being a local tip phenomena

You've read good
This picture (Wikipedia) summarises in a perfect way what you've read:

From the whole trailing edge of the wing a vortex (red line) is shed everywhere lift changes along the span of the wing. The strength of the vortex is proportional to this local change in the lift.
All those vortices eventually come together to form one big vortex which is the tip-vortex proper.

Does this mean I am obliged to model the entire wing?

Yes, unless the biggest changes in the spanwise lift happen only on a limited part of the wing: this is for example a common simplification for rotor blades, where the biggest change in lift happens at the tip and then only the tip vortex (or better, the vortex at the tip) can be simulated.

But this makes the simulation much more expensive!

If you are modelling only the wing with its wake, a simple panels method runs in a couple of minutes.

the tip vortex comes from the roll-up of the entire sheet as opposed to being a local tip phenomena

One might question that statement.  Aircraft, especially large and heavy, form large trailing vorticies from their own downwash.  These vorticies result from the ambient air being drawn into the downwash flow.
A wing tip vortex is much smaller and far less energetic.  It is indeed a local phenomena resulting from the pressure differential of upper and lower wing.
This means that, while there can be efficiency gains with modified wingtips under certain flight regimes, trailing vorticies from lift creation cannot be eliminated.
As far as modeling the entire wing, yes, this would provide useful information on energy balances.  One might start with a seagull or albatross wing, or perhaps the DC-3.
These wings are very efficient, but suffer tip stall issues.  Slats help make these wings safer.

By no means am I an expert on the topic, but this should be some good info for you. To answer your question directly, yes, you can just model like 1/3 of the wing. I’ve seen tons of models doing just that for wing tip purposes. Modeling in the aspect you are looking for (at least from what I can tell) is more learning based so modeling the main part you are looking to see shouldn’t be a big issue as long as you’re modeling enough to get your answer. Ideally, you’d want to get a whole model of the wing for the most data backed answer. Attached is a link of a partial wing for a tip vortex modeled how you were thinking! There are many more like this.

Side comment: this simulation is the result of exascale computation ( https://en.wikipedia.org/wiki/Exascale_computing ). Modelling 1/10 instead of 1/3 of the wing is of limited help, if you still need 10'000s xeon cpus...
To OP: the boundary conditions you would like to impose on the near tip field needs to have certain temporal/statistical properties to mimic the results of this large scale model. It is an extremely simple question to be posed: when does laminar flow transition to turbulent flow?
To give an answer, however, it is one of the biggest open problem in physics/mathematics ...